In an interview during the Group of Eight Energy Ministers meeting in Japan, Gary Lunn said Washington has signaled to Canada that issues arising from the U.S. Energy Independence and Security Act will be "addressed and resolved."

The law, which was passed in December, has a provision preventing federal agencies from buying "alternative or synthetic" fuels with higher greenhouse gas emissions than conventional fuels.

Canada is the biggest supplier of crude oil to the U.S., with an increasing proportion coming from Alberta's vast oil sands. But extracting and processing the sludgy bitumen is an energy- and emissions-intensive business, estimated to emit around three times as much greenhouse gas as extraction of conventional crude oil.

The legislation provoked a diplomatic flurry, with the Canadian ambassador to the U.S. warning of "unintended consequences" should the contentious section 526 block oil sands exports.

"We've raised these issues with Washington and we received very positive feedback from (U.S. Energy) Secretary Bodman," he said.

Output from Alberta's oil sands resources, the world's second-biggest crude reserve after Saudi Arabia, is expected to triple to more than 3 million barrels a day in 2015. The bulk of this production is destined for the U.S., and several pipeline projects are underway to reinforce these links.

Canada displaced Saudi Arabia as the top U.S. supplier of crude oil in 2004, and in 2007 accounted for nearly 19% of U.S. imports, according to the U.S. Energy Information Administration. Canadian officials have said that about half of the 1.8 million barrels a day of crude Canada ships to the U.S. daily comes from oil sands.

Lunn said the U.S. recognized the efforts that Canada is making in tackling emissions of greenhouse gases produced by oil sands development and other sources.

Canada has launched the world's first fully integrated clean coal electricity project with full carbon sequestration, he said.

In addition, the country has imposed standards on all new oil sands development, specifically that projects coming online after 2012 will have to be able to capture emissions and store them underground by 2018.